generally, try going into your printer properties (start> control panel> printers and other hardware>select that printer>PROPERTIES) and check each tab (if there are more than one) looking specifically to see if there is a check mark or the 'radio button' is selected on an option that says something like 'fit to one page', or 'fit to page', etc.

An even quicker 'fix' would be to see if you have an option in the properties to reset all settings to default-- which would return any changes made to where they were when you first used the printer.